Table Of ContentContents
Credits 5
Chapter 1 IntroduCtIon 6
Mammals 6
Types of Marine Mammals 8
Ungulates and Carnivores 8
Reptiles 9
Types of Marine Reptiles 9
Characteristics of Marine Reptiles 9
Chapter 2 aquatIC ungulates 11
Order Cetacea 11
Habitat and distribution 11
Physical characteristics and physiology 12
Digestion 13
Reproduction 13
Behaviour 13
Echolocation 14
Significance to man 14
The Order Cetacea 15
Suborder Mysticeti (Baleen Whales) 15
Suborder Odontoceti (Toothed Cetaceans) 15
More Information about the Suborder Mysticeti (Baleen Whales) 16
More Information about the Suborder Odontoceti (Toothed Cetaceans) 22
Dolphins 23
Whales 34
The Order Sirenia 35
Chapter 3 MarIne CarnIvores 38
Pinnipeds 38
Walrus 38
True Seals and Fur Seals 38
Marine and Sea Otters 41
Polar Bear 42
Chapter 4 MarIne reptIles 43
Sea Turtles 43
Taxonomy (Classification) 44
Extinct Marine Turtles 51
Crocodiles 52
Differences Between Gharials, Alligators, and Crocodiles 53
Extinct Marine Crocodiles and Crocodile-Like Groups 56
Marine Lizards 57
Modern Marine Iguanas 57
Extinct Marine Lizards 59
Marine Snakes 60
File Snakes 61
Extinct Marine Snakes 68
Further reading and study 69
More ebooks available 69
Courses available 69
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The information in this book is derived from a broad cross-section of resources
(research, reference materials and personal experience) from the authors and editorial
assistants in the academic department of ACS Distance Education. It is, to the best
of our knowledge, composed as an accurate representation of what is accepted and
appropriate information about the subject, at the time of publication.
The authors fully recognise that knowledge is continually changing, and awareness
in all areas of study is constantly evolving. As such, we encourage the reader to
recognise that nothing they read should ever be considered to be set in stone. They
should always strive to broaden their perspective and deepen their understanding of
a subject, and before acting upon any information or advice, should always seek to
confirm the currency of that information, and the appropriateness to the situation in
which they find themselves.
As such, the publisher and author do not accept any liability for actions taken
by the reader based upon their reading of this book.
published by:
ACS Distance Education
P.O. Box 2092, Nerang MDC,
Queensland, Australia, 4211
[email protected]
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ISBN: 978-0-6483232-9-7
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CredIts
photos: John Mason
layout: Stephen Mason
editorial Contributors:
Kara Wight B.Sc., HND (Animal)
Dr Maria L. Schmitz Fontes PhD, MSc, BA
Peta Jinnath Abdul B.Sc.Grad.Dip.Ed.
Jacinda Cole BSc, M.Psych
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Chapter 1 IntroduCtIon
We are more familiar with land animals, quite naturally, because that
is where humans live. Marine environments may not be as familiar
to most people, but they do contain as great a diversity of animals
as are found on land. Marine animals can vary from tiny single
celled organisms through to the largest animals on earth. Fish and
crustaceans are obvious to us. There are more complex animals than
fish and crustaceans though which also inhabit marine environments;
including birds (e.g. seagulls and penguins), mammals and reptiles.
While the birds are never exclusively confined to the water; there are
reptiles and mammals which spend almost all, or even all of their time
in the water.
The most familiar marine mammals
MaMMals
include seals, sea lions, dolphins,
and whales. Each of these mammals,
Marine mammals are mammals however, is specially adapted to live in
that have adapted to the marine an aquatic environment. For example,
environment. This means that they both dolphins and whales are born with
share the same characteristics as all a smattering of hair; many lose these
other mammals: quickly during the first few days of life.
Some, like adult humpback whales,
● birthing live young have hair follicles along the skin.
● suckling young from mammary
glands or adapted mammary patches
● endothermic
● four-chambered hearts
● air-breathing
● hair and/or fur at some stage in the
lifecycle
Marine mammals are found throughout
the world. Research suggests that
around 40% of marine mammals live
around 40 degrees north and south of
Australian fur seal
the equator.
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Indo Pacific humpback Dolphin
Many marine mammals have lost the Other species such as polar bears
ability to move about efficiently on land. have thick layers of fat and fur to help
Pinnipeds, such as seals, live parts them maintain their body heat in cold
of their lives on land, but hunting and climates, a large body to help keep
food gathering behaviours are generally them warm and disperse their body
performed in a marine environment. All heat, thick curved claws for gripping
marine mammals, even those which live the ice and predators, sharp teeth
entirely in the sea, must breathe air. This and strong jaws for tearing apart prey
means that animals such as dolphins and and powerful muscles for fighting and
whales must surface regularly. Generally, attacking. Although polar bears do not
they do not need to bring the entire body live their whole lives in the water, they
– or even the entire head – above water. are considered marine mammals due to
their dependence on the water for food
Other marine mammals, like whales, and living environment. Polar bears are
dolphins, and porpoises, have lost the only bears considered marine, and
their fur-covering and developed to live in such extreme environs.
streamlined bodies. This reduces drag
when swimming, allowing them to slice
quickly through the water. Lungs are
also specialised, and lungs and muscles
can store oxygen, allowing them to stay
underwater. Many marine mammals
also have layers of thick blubber or
fat to help maintain body heat in cold
environments. Colder environments can
also affect blood flow, which means many
marine mammals have enlarged veins to
help transfer blood to vital organs. Limbs
are also adapted, with flippers, flukes,
A whale skeleton showing its ungulate
and fins assisting in movement through
characteristics
a more viscous environment.
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Some scientists group sea otters and
polar bears together into a group called
fissipeds (split toes).
ungulates and Carnivores
Marine mammals can also be divided
into two main groups: the ungulates
and carnivores. Ungulates are “hoofed”
mammals, while carnivores are
meat eaters.
Marine ungulates
Most ungulates are land animals,
such as goats and camels. Recent
research, however, suggests that some
marine mammals are descended from
a common ungulate ancestor. These
include the cetaceans and sirenians.
Cetaceans
Toothed whale skeleton (Odontoceti)
● whales
types of Marine Mammals
● dolphins
There are several distinct marine
mammal groups. It is important to note, ● porpoises
however, that classification is an ongoing
process – as scientists learn more about sirenians
the genetic makeup of different animals’
species are reclassified, with some ● manatees
higher-ranking groups added or moved.
Overall, marine mammals are divided ● dugongs
into five distinct groups:
It is important to note, however, that many
● pinnipeds researchers still do not class cetaceans
as ungulates, especially since they lack
● cetaceans many other ungulate characteristics.
Moreover, cetaceans are carnivores,
● sea otters while the majority of ungulates are either
herbivorous or omnivorous.
● sirenians
In most cases, “marine ungulate”
● polar bears refers to the sirenians, all of which
are herbivorous.
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Sea Snake
reptIles Characteristics of
Marine reptiles
There are some major characteristics
of marine reptiles – characteristics they ● ectothermic
share with land reptiles. The major
difference is that marine reptiles have ● some keratinous scaling
adapted to aquatic or semi-aquatic
environments. ● lung-based respiration
(as opposed to gills)
types of Marine reptiles
Marine reptiles are an important –
Although there are many marine reptiles and fascinating – group. There is
in the fossil record, there are only a great diversity among marine reptiles,
handful of groups that are true living and many kinds are found all over the
(extant) marine reptiles. Although some globe. While many people think of
people call crocodiles marine reptiles, it all reptiles as egg-laying (oviparous),
is important to note that “marine” refers many reptiles are in fact viviparous,
to the sea, and with the exception of giving birth to live young. This is seen
the saltwater crocodile, crocodiles are in almost all true sea snakes (elapids)
adapted for freshwater. In the context and is quite possibly an adaptation to
of this book, marine can also include the marine environment. Most likely due
brackish and estuarine environments, to the complexity of in vivo gestation,
though this is also specifically noted sea snake litters are relatively small
throughout. – ranging up to around 40 young. By
contrast, oviparous snakes, which lay
● sea snakes eggs, may lay up to 100 eggs at a time,
usually in a single clutch.
● sea turtles
Marine reptiles, such as the crocodilians
● marine lizard (marine iguana) and sea turtles, are some of the oldest
animals on earth. This group has well-
● crocodilians adapted hunting behaviours, and in
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the case of crocodilians and turtles, defence. This has made them successful
protective coverings and strong swimming enough to outlive many other species.
adaptations that help in both attack and
Green turtle
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